The possible role of motor development on psychological function is once again a topic of great theoretical and practical importance. The revival of this issue is stemming from a different approach to the topic, away from Gesell's interest in the long-term prediction of psychological functions from early motoric assessments,toward an attempt to understand how locomotor experience orchestrates psychological changes. Research to date is quite promising in pointing to a linkage between crawling experience and cognitive, perceptual, social, and emotional changes. However, this work, having been conducted within a quasi-experimental framework, is intrinsically limited in its contributions, despite its heuristic implications for normal and clinical populations and for brain development. Enough research has been conducted with positive findings, however, to warrant the difficult but necessary task of determining whether crawling experience is playing a causal role as an inducer or facilitator of psychological development or whether it is a maturational forecaster - a sign of important psychological changes to come. This proposal describes an experimental approach to addressing the potential role of locomotor experience on the development of sensitivity to peripheral optic flow. Three experiments are proposed in which locomotor experience is manipulated in a powered-mobility-device and developmental changes in sensitivity to peripheral optic flow are measured on the basis of infants postural compensations to side wall movement in a moving room. Experiment 1 focuses on the efficacy of infants~ ability to control the powered-mobility-device and the consequent changes in sensitivity to peripheral optic flow that result from self generated experiences in such a device. Experiment 2 examines the role of active versus passive experiences in the mobility device and consequent changes in sensitivity to peripheral optic flow, whereas Experiment 3 looks at whether differential attentiveness to the environment while locomoting contributes to the aforementioned perceptual changes.